Observational constraints on the first indirect aerosol effect
Ralf Bennartz
Atmospheric & Oceanic Sciences
University of Wisconsin - Madison
Acknowledgements
Rene Preusker
Lothar Schüller
Chris O’Dell
Amato Evan
FU-Berlin
EUMETSAT
UW-Madison
UW-Madison
Brent Maddux
Lori Borg
UW-Madison
UW-Madison
Albedo parameterization
Indirect aerosol effect
Diurnal cycle of LWP
Diurnal cycle of CF
Data
Data
IPCC 2007
IPCC 2001
Microphysical changes due to pollution
Data
•
Cloud liquid water path diurnal cycle (O’Dell et al., 2007, J
Climate, in press)
•
Cloud fraction diurnal cycle (ISCCP)
•
Cloud droplet number concentration (CDNC) (MODIS,
Bennartz, 2007, JGR)
•
Aerosol & fine mode fraction (used as proxy for natural
background fraction of CDNC)
•
Cloud droplet number concentration from MODIS
The diurnal cycle of clouds
Local Time [hours]
The diurnal cycle of clouds
Liquid Water
Path [kg/m2]
Local Time [hours]
The diurnal cycle of clouds
Liquid Water
Path [kg/m2]
Low Cloud
fraction
Local Time [hours]
The diurnal cycle of clouds
Liquid Water
Path [kg/m2]
Low Cloud
fraction
Local Time [hours]
Reflected
Solar Flux
How does our albedo compare to observations (CERES)?
Anthropogenic fraction: Note: This is a proxy
IAE
This study
(Chen and Penner, 2005, ACP)
Conclusions
IPCC 2007
Conclusions
IPCC 2007
Land
N to first order a
function of
anthropogenic
aerosol optical
thickness
Different behavior
for different
continents at high
anthropogenic
fraction
Ocean
(
)
N = 20 + 35 ⋅ ⎡ log10 ( cchlorophyll ) + 2 ≥ 0 ⎤ + 104 ⋅
⎣
⎦
τ anth , proxy
τ